Copolymers of ethylene with tetrafluoroethylene [ETFEs] have well balanced thermal, chemical, mechanical, and electrical properties. Therefore, ETFEs are used in the field where heat resistance and chemical resistance are needed, specifically used for electrical wire covering, tubes, hoses, sheets, and the like.
However, ETFEs problematically tend to crack. In order to solve such a problem, methods for suppressing the generation of cracks by introducing a small amount of third monomer into copolymers have been examined.
Patent Document 1 discloses an ethylene/tetrafluoroethylene copolymer produced by polymerizing a supplemental amount of copolymerizable vinyl monomer which has no telogen activity and provides into the copolymer a side chain containing two or more carbon atoms.
Example IX discloses the embodiment in which CF2═CF—O5F11, CF2═CF—C2F5, or the like is polymerized as a vinyl monomer.
Patent Documents 2 and 3 each disclose in Example 2 a copolymer having a molar ratio of tetrafluoroethylene/ethylene/perfluorohexylethylene of 53/46.3/0.7. Patent Document 2 discloses in Example 4 a copolymer having a molar ratio of tetrafluoroethylene/ethylene/perfluorobutylethylene of 53/45.5/1.5.
Patent Document 4 discloses an ethylene/tetrafluoroethylene copolymer having a molar ratio of tetrafluoroethylene/ethylene of 50-60/50-40, including a fluorine-containing vinyl monomer copolymerizable with ethylene and tetrafluoroethylene, and having a volumetric flow rate of 10 to 300 mm3/sec. The fluorine-containing vinyl monomer mentioned above is particularly preferably CH2═CH—C4F9, and the amount of the fluorine-containing vinyl monomer is particularly preferably 2.5 to 5.0 mol %.
Patent Document 1: JP 47-23671 B
Patent Document 2: JP 54-033583 A
Patent Document 3: JP 54-132692 A
Patent Document 4: JP 7-041522 A